1. Field of the Invention.
This invention relates in general to data storage devices, and more particularly to an improved labyrinth seal for minimizing flow gradients leading to the release of contaminants.
2. Description of Related Art.
In data storage devices, bits representing data are recorded on a storage medium. For example, in a disk drive, data bits are stored in circular tracks on rigid or flexible disks which are rotated at relatively high speeds. Bits are written or read by a read/write head which must be accurately positioned relative to the particular track which is being written or read. This means that the disks must rotate without wobble so that the radial displacement of the track with respect to the head position is eliminated or at least minimized.
To impart rotation to such disks it is known to arrange the electric drive motor axially near the disk and to connect the disk via suitable connecting elements to the motor shaft for rotation therewith. However, problems sometimes occur due to dirt particles when writing or reading out data. Dirt particles may emanate from the bearings and the winding. In particular, grease or dust particles can escape from the bearing system. The spindle motors in disk drives can thus experience aerosoling of grease/oil particles from the spindle bearings. This aerosoling can cause contamination of the head disk interface resulting in reduced near term or long term file reliability.
Contaminants have been confined by complicated and expensive seals. Rotary seals have for years been conventionally disposed between the rotating and stationary components of rotary machines to impede the leakage of a fluid medium therebetween. For example, labyrinth seals are typically implemented in the design of many spindles to prevent the occurrence of aerosoling.
Labyrinth seals are formed of a scaling surface or land on one component and a restrictive ring on an opposing component wherein the ring projects into close proximity with the land. A plurality of restrictive rings are commonly required in series to provide sufficient sealing. The term "seal" as used herein refers to a tight closure, albeit not a perfect closure as totally against the passage of air. Thus, the labyrinth seal can provide a seal using intricate paths that inhibit, if not prevent, the outward movement of contaminant particles from the motor. Such labyrinth seals make it possible to considerably reduce the risk of dirt particles passing from the inside of the motor into the area of the storage disk so that problems occurring when writing or reading out data is minimized.
Nevertheless, a natural flow gradient does develop between the rotating and stationary elements of the spindle/labyrinth seal. Small leaks within the spindle or pressure gradients in the file can assist in changing the flow gradient to cause leakage through the seal to the interior of the hard drive assembly. For example, 10-15% fallout for aerosoling under dynamic conditions has been observed.
It can be seen that there is for an improved labyrinth seal that minimizes flow gradients leading to aerosoling of contaminants external to spindles.